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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * The Universal Permissive License (UPL), Version 1.0
 *
 * Subject to the condition set forth below, permission is hereby granted to any
 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
 * copyright rights in the Software, and any and all patent rights owned or
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 * unmodified Software as contributed to or provided by such licensor, or (ii)
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 *
 * (a) the Software, and
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 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
 * is contributed by such licensors),
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 * without restriction, including without limitation the rights to copy, create
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 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
 *
 * This license is subject to the following condition:
 *
 * The above copyright notice and either this complete permission notice or at a
 * minimum a reference to the UPL must be included in all copies or substantial
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package com.oracle.truffle.api.bytecode;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import com.oracle.truffle.api.CallTarget;

/**
 * Annotation indicating a parameter that takes zero or more values. If the final parameter of an
 * operation is annotated with {@code @Variadic}, those values will be collected into an
 * {@code Object[]} as the last argument.
 * <p>
 * This annotation can also be applied to an {@link Operation} class to mark its return type as
 * variadic. Such return values are flattened into the variadic array when used as one or more
 * operands to a {@link Variadic} parameter. All specializations of a variadic-return operation must
 * always return a non-null {@link Object[]} value.
 *
 * @since 24.2
 */
@Retention(RetentionPolicy.SOURCE)
@Target({ElementType.PARAMETER, ElementType.TYPE})
public @interface Variadic {

    /**
     * Specifies the number of values reserved in the variadic object array. The array is sized
     * accordingly, which can be useful when passing variadic arguments to a
     * {@link CallTarget#call(Object...) call} without reallocating the array.
     *
     * <pre>
     * &#64;Operation
     * static final class FunctionCall {
     *     &#64;Specialization
     *     public static Object variadic(CallTarget target, Object function,
     *                     &#64;Variadic(startOffset = 1) Object[] args,
     *                     &#64;Cached IndirectCallNode callNode) {
     *         args[0] = function; // use index 0 for the function instance
     *         return callNode.call(target, args);
     *     }
     * }
     * </pre>
     *
     * @since 25.0
     */
    int startOffset() default 0;

}
